In virtual reality ("VR"), the sensation of motion is coordinated with the senses of sight, sound, and even touch. The "environment" that a person experiences is manufactured and contained in the silicon of computer processors and memory. Flight simulators used for training professional pilots and astronauts are a type of virtual reality system commonly in use today. As technology advances, the applications for "virtual reality" have grown well beyond such expensive, specialized equipment and are anticipated as being increasingly common as home entertainment or learning devices.
Although the hardware and software for generating the audio and visual components of virtual reality systems has been decreasing in cost, motion systems for use with such components to complete a virtual reality system have consistently been prohibitively expensive. Furthermore, the motion systems are either too complex, limited in their freedom of motion, or lack adequate responsiveness.
Various devices have been proposed for generating motion. U.S. Pat. No. 4,489,932, for example, describes a sphere resting on three passive casters, with motion of the sphere being actuated either by the user shifting his weight inside the sphere or by a multi-directional drive wheel. Another device for generating motion is found in U.S. Pat. No. 4,545,574, which discloses a sphere supported by an air stream moving within a large tube where the sphere is rotatable by louvers directing the force of the air around the sphere. Although both U.S. Pat. Nos. 4,489,932 and 4,454,574 describe a sphere rotatable about the three orthogonal axes at the center of the sphere, these devices cannot move the center of the sphere with respect to the external environment, i.e. they are not capable of linear motion. Moreover, these devices described in these patents also lack an interactive system coordinating motion, sight, and sound.
Other patents have proposed simulated motion devices which coordinate motion with audio and visual input. U.S. Pat. No. 3,135,057, for example, shows a capsule disposed within heavy inertial rings offset at 90.degree. from one another. U.S. Pat. No. 4,856,771 shows a system that coordinates motion, video, and sound by using a cockpit situated inside two rings that are offset by 90.degree. where the rings rest on a rotatable base. U.S. Pat. No. 5,060,932 describes a large gyroscope-like device where various means of visual and aural stimulations are provided. Although U.S. Pat. Nos. 3,135,057, 4,856,771, and 5,060,932 describe motion devices that combine motion with audio and visual input, they all are limited in their applicability to virtual reality systems because of their slow response or large expense.
U.S. Pat. No. 4,908,558 describes a spherical motion simulator mounted on a stationary frame for angular and translational movement along pitch, roll and yaw axes. Magnetic bearing supported by the stationary frame provide three degrees of freedom. Drive means mounted on the stationary frame and connected to the test unit generate three degrees of freedom of movement.
U.S. Pat. No. 5,071,352 describes a motion platform with limited translational and rotational motion. An arrangement of three linear actuators is combined with an A-frame type restraining mechanism to allow rotation about the pitch and roll axes and along a vertical axis. A multiple-user capsule sits on a rigid frame and users view images and experience sound in coordination with motion.
Current devices for simulating motion are cumbersome and expensive. As a result, the devices have slow response times. Moreover, these devices are limited in their ability to provide linear and rotational motion about three orthogonal axes.
A major limitation in state-of-the art VR is the inability to permit simple walking and running. Navigation is typically experienced as a disembodied center of consciousness which is directed by pointing, other gesture or by manipulation of a joystick, trackball, mouse, or similar device. The actual physical sensation of walking is limited to one of two forms: a) The user is restricted to a confined and immobile surface where tracking and signal generation are well-controlled, and b) the user is confined to device such as a linear treadmill or wheelchair which transduces the user's linear motion to virtual space navigation. The conventional linear treadmill has a movable track which can be upwardly inclined. The track is only movable in one direction which restricts motion of the user to the direction of movement of the track. A monitor, such as a motivational electric display, associated with the track, records the time, speed, and distance accomplished by the user.
Use of a linear treadmill, consisting of one continuous moving track, in conjunction with a monitor permits a user to walk in a straight line. The user cannot step in arbitrary directions as he or she would be able to in real life. This limitation in directionality detracts from the immersive nature of the experience, and requires that the experience take on more of a vehicular nature rather than freely walking and navigating body.